The fuel cell electrode catalyst currently in use may have deterioration such as durability reduction. Particularly, a cathode carbon support catalyst in the fuel cell may corrode due to harsh condition such as driving process, frequent start and stop of a vehicle. For example, in the fuel cell of the vehicle, corrosion of the carbon support catalyst may be caused by generation of high voltage at the time of start and stop during vehicle driving, and contact between the electrode catalyst and reaction gas may deteriorate by water generated at the cathode during fuel cell operation, and thus the operation may depend on carbon fuel instead of oxygen fuel.
Generally, a catalyst such as a Pt/C catalyst has been applied to the cathode carbon support in the fuel cell. In addition, for inhibiting the corrosion of the carbon support catalyst, a method has been developed to use specific metals, for example, iridium (Ir) and ruthenium (Ru), which is belongs to a precious metal, and the catalyst obtained from the method using the precious metal may have substantially improved water-splitting power at the voltage (1.6 V) from platinum (Pt) in the general Pt/C catalyst.
In addition, in the related arts, when Oxygen Evolution Reaction (OER, water-splitting catalyst), i.e, oxides such as IrO2 or RuO2 to the Pt/C electrode is used by mixing thereof to the electrode, durability of the catalyst may generally increase (Sang-Eun Jang and Hansung Kim. (2010, Effect of Water Electrolysis Catalysts on Carbon Corrosion in Polymer Electrolyte Membrane Fuel Cells, J. Am. Chem. Soc., 132, 14700-14701). Further, a method for manufacturing a platinum/ruthenium alloy support catalyst has been reported and the method comprises: mixing a platinum precursor, a ruthenium precursor and a solvent and adjusting pH, mixing a catalyst carrier solution to the resulting mixture and adjusting pH, and then separating, washing and heating the catalyst.
However, the Ru or its oxides may not be suitable since they may have a defect of easy dissolution due to low phase stability at acidic operating condition such as Proton Exchange Membrane Fuel Cell (PEMFC). In addition to the Ru oxide, such defect may occur with alloy-type of Pt or Ru such that metal may disappear by continuous dissolution during operation of the fuel cell. Accordingly, when the fuel cell includes the Ru, the first Oxygen Evolution Reaction (OER) may be sufficient but the activity of the Oxygen Evolution Reaction may be reduced as low as 0 from the second cycle.
In the related art, platinum-iridium alloy particles have been developed. The alloy particles may be formed by calcining a conductive carrier and particles may have platinum and iridium supported on the conductive carrier. Further, a method for manufacturing a catalyst by adding a precursor containing metal ion such as Pt and Ir to ethylene glycol and reducing the mixture thereof has been introduced. In addition, a method for manufacturing a catalyst for a fuel cell has been developed and the method comprises mixing a main catalyst metal precursor, a metal precursor such as iridium as a co-catalyst and a diol compound such as ethylene glycol, adding a carbon support thereto, reducing thereof by using a reducing agent, and then purifying and drying the resulting material.
However, although the above mentioned techniques may provide improvement by applying iridium and the like, methods of manufacturing a product having improved durability have not been achieved yet. For example, process condition has not been improved due to long charge stabilizing time and difficulty to manufacture homogeneous support.
Accordingly, the present invention provides an alloy catalyst which may be manufactured by alloying iridium to the platinum contained in a cathode carbon support catalyst for a fuel cell at a predetermined process and condition, thereby inhibiting corrosion, reducing time for stabilizing carbon zeta-potential, and controlling metal particle size. As consequence, high quality products having uniform metal particle distribution and excellent durability may be obtained.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.